Violet Camille, Parkinson Makenna, Ball Akash K, Kulik Heather J, Fortner John D, Elimelech Menachem
Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520-8286, United States.
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States.
ACS Appl Mater Interfaces. 2025 Jan 8;17(1):1911-1921. doi: 10.1021/acsami.4c16173. Epub 2024 Dec 16.
The pressing demand for critical metals necessitates the development of advanced ion separation technologies for circular resource economies. To separate transition metal ions, which exhibit near-identical chemical properties, adsorbents and membranes must be designed with ultraselective chemistries. We leverage the customizability of metal-organic frameworks (MOFs) to systematically study the role of material chemistry in sorption and selectivity of Co, Ni, and Cu. To isolate the effect of MOF linker chemistry, a series of functionalized UiO-66 derivatives was synthesized from the same parent MOF through solvent-assisted linker exchange, which produced >70% linker conversion for nine linker functional groups. This work presents the first instance of post-synthetic incorporation of carboxylic acid groups in UiO-66, which was achieved with >90% conversion. A technique was developed for MOF deposition in a quartz crystal microbalance to precisely monitor real-time sorption of Co, Ni, and Cu in UiO-66-X [where X = H, (OH), COOH, or (COOH)] and validated by comparing to batch sorption experiments (5 mM, pH 5). Carboxylic acid-functionalized derivatives exhibited the highest uptake and a trend of Cu > Co > Ni, with the highest sorption of 5.5% (g Cu/g MOF), equivalent to 37% mol Cu/mol linker, occurring in UiO-66-(COOH). Binary salt and single salt batch sorption experiments demonstrated preferential copper binding in all studied MOFs and selectivity enhancement in binary salt conditions. UiO-66-(COOH) exhibited the highest selectivity of 14 for equimolar Cu/Ni and 13 for Cu/Co. Density functional theory calculations of ion binding energy at UiO-66-X pore windows indicate higher copper affinity for all functional groups and a trend in binding energy of UiO-66-(COOH) > UiO-66-COOH > UiO-66-(OH) > UiO-66-H for each transition metal ion, in good agreement with experimental results. This work highlights the effectiveness of post-synthetic modification for tuning nanostructured materials to achieve similar ion separations.
对关键金属的迫切需求使得开发适用于循环资源经济的先进离子分离技术成为必要。为了分离化学性质近乎相同的过渡金属离子，必须设计具有超选择性化学性质的吸附剂和膜。我们利用金属有机框架（MOF）的可定制性，系统地研究材料化学在钴、镍和铜的吸附及选择性方面的作用。为了分离MOF连接体化学的影响，通过溶剂辅助连接体交换，从同一母体MOF合成了一系列功能化的UiO-66衍生物，九个连接体官能团的连接体转化率超过70%。这项工作首次实现了在UiO-66中通过后合成法引入羧酸基团，转化率超过90%。开发了一种在石英晶体微天平中沉积MOF的技术，以精确监测UiO-66-X[其中X = H、(OH)、COOH或(COOH)]中钴、镍和铜的实时吸附情况，并通过与批量吸附实验（5 mM，pH 5）进行比较来验证。羧酸功能化衍生物表现出最高的吸附量，以及铜>钴>镍的趋势，在UiO-66-(COOH)中最高吸附量为5.5%（克铜/克MOF），相当于37%摩尔铜/摩尔连接体。二元盐和单盐批量吸附实验表明，在所有研究的MOF中铜具有优先结合性，并且在二元盐条件下选择性增强。UiO-66-(COOH)对等摩尔铜/镍的选择性最高，为14，对铜/钴的选择性为13。在UiO-66-X孔窗口处离子结合能的密度泛函理论计算表明，对于所有官能团，铜的亲和力更高，并且对于每种过渡金属离子，UiO-66-(COOH)> UiO-66-COOH > UiO-66-(OH) > UiO-66-H的结合能呈趋势变化，与实验结果高度吻合。这项工作突出了后合成修饰在调整纳米结构材料以实现类似离子分离方面的有效性。
